1. Field of the Invention
The present invention relates to an image pickup apparatus which is capable of picking up a still image and a moving image and displaying a image representing an object brightness that can be set as a target exposure by exposure control, and a method of controlling the same.
2. Description of the Related Art
Conventionally, an image pickup apparatus (camera) is configured such that a user can set an aperture value (Av value) and a shutter speed (time value: Tv value). For example, when the user selects an exposure mode in which the user sets an Av value and the camera performs shooting after changing the shutter speed and the ISO sensitivity (photographic sensitivity) (this exposure mode will be hereinafter referred to as “the Av priority mode”), a conventional camera performs control as follows: When ambient brightness changes and any of the shutter speed and the ISO sensitivity reaches its limit value, a shutter speed display section provided on a camera main unit is caused to flash on and off so as to warn the user that the Av value is out of an interlocking range, or the Av value is automatically changed to a value other than a set value, so as to obtain correct exposure.
Further, for example, when the user selects another exposure mode in which the user sets a shutter speed and the camera performs shooting after changing an Av value and an ISO sensitivity (this exposure mode will be hereinafter referred to as “the Tv priority mode”), the exposure control is performed by replacing the Av value in the Av priority mode with the shutter speed. It should be noted that the term “interlocking range” is intended to mean respective ranges of Av values, Tv values and ISO sensitivities within each of which the camera can automatically set an associated one of an Av value, a Tv value and an ISO sensitivity in a fashion interlocked with the others such that correct exposure is obtained.
On the other hand, as a technique related to the above-described camera control, there has been proposed the following technique (e.g. Japanese Patent Laid-Open Publication No. 2005-115060). According to Japanese Patent Laid-Open Publication No. 2005-115060, in a combination of a camera which is capable of automatically setting an ISO sensitivity and a flash unit (strobe), the upper and lower limit values of ISO sensitivity and an Av value, which can be set, are sent from the camera to the flash unit, and the flash unit displays a interlocking range for lighting control defined by also taking into account a range of ISO sensitivities.
In the conventional technique described above, a warning is displayed when any of parameters changed by the camera, except the Av value or the shutter speed set by the user, falls out of its interlocking range. However, there remains a problem of actual exposure causing overexposure (which makes an entire image whitish) or underexposure (which makes an entire image blackish).
Further, in the conventional technique, when any of the parameters changed by the camera, except the settings configured by the user, falls out of its interlocking range, the camera automatically performs control for changing the settings, so that correct exposure can be obtained. However, it is impossible to obtain an image creating effect, such as a blur effect (adjustment of the degree of blur of a background) as intended by an Av value initially set by the user and a stop effect (moving object taken as an image in a still state or in a blurred state) as intended by a shutter speed initially set by the user.